1. Technical Field
The present disclosure relates generally to radio frequency integrated circuits, and more particularly, those fabricated with complementary metal oxide semiconductor (CMOS) technology. The present disclosure also relates to a high gain, low noise figure low noise amplifiers with low current consumption.
2. Related Art
Wireless communications systems are utilized in a variety contexts involving information transfer over long and short distances alike, and a wide range of modalities for addressing the particular needs of each being known in the art. As a general matter, wireless communications involve a radio frequency carrier signal that is variously modulated to represent information/data, and the encoding, modulation, transmission, reception, de-modulation, and decoding of the signal conform to a set of standards for coordination of the same.
Many different mobile communication technologies or air interfaces exist, including GSM (Global System for Mobile Communications), EDGE (Enhanced Data rates for GSM Evolution), and UMTS (Universal Mobile Telecommunications System) W-CDMA (Wideband Code Division Multiple Access). More recently, 4G (fourth generation) technologies such as LTE (Long Term Evolution), which is based on the earlier GSM and UMTS standards, are being deployed.
Besides these mobile communications modalities, there are local area wireless data networking modalities such as Wireless LAN (WLAN)/Wi-Fi, WiMax, and so forth. Several computer systems or network nodes within a local area can connect to an access point, which in turn may provide a link to other networks and the greater global Internet network. Computing devices of all form factors, from mobile phones, tablets, and personal computers now have Wi-Fi connectivity, and Wi-Fi networks may be found everywhere.
A fundamental component of any wireless communications system is the transceiver, that is, the combined transmitter and receiver circuitry. The transceiver encodes the data to a baseband signal and modulates it with a radio frequency carrier signal. Upon receipt, the transceiver down-converts the radio frequency signal, demodulates the baseband signal, and decodes the data represented by the baseband signal. An antenna connected to the transmitter converts the electrical signals to electromagnetic waves, and an antenna connected to the receiver converts the electromagnetic waves back to electrical signals.
The output of the transmitter is connected to a power amplifier, which amplifies the outgoing radio frequency signals prior to transmission via the antenna. The receiver is connected to the output of a low noise amplifier, the input of which is connected to the antenna and receives incoming radio frequency signals. Depending on the particulars of the communications modality, single or multiple antennas may be utilized. A transmit/receive switch selectively interconnects the antenna(s) to the output of the power amplifier during transmission, and to the input of the low noise amplifier during reception. Additionally, there may be a power detector circuit to measure the output power to control variable gain blocks in the transceiver chain. Thus, the power amplifier, the low noise amplifier, the antenna switch(es), and the power detector serve as key building blocks in radio frequency transceiver circuitry.
In order to lower manufacturing costs and allow full integration of a complete radio frequency System-on-Chip (SoC) capable of multimode and multiband operation, complementary metal oxide semiconductor (CMOS) technology is utilized. The low noise amplifier, the antenna switches, and the transceiver radio frequency circuit are thus being implemented on a single integrated circuit die. Such silicon-based single chip systems are dominant in GSM, WLAN, Bluetooth, WCDMA, and LTE applications. Furthermore, advancements in nanometer-level semiconductor fabrication, together with increasing device unity power gain frequency (fmax), CMOS technologies have become a viable low-cost option for highly integrated radio frequency products utilized in the most popular applications.
A challenge with radio frequency system-on-chip implementations is the requirement of extremely low noise figures, low current consumption, and low insertion loss with respect to the low noise amplifier. Most conventional mobile devices employ a standalone low noise amplifier with a single pole, multiple throw (SPnT) switch fabricated with Silicon Germanium (SiGe) heterojunction bipolar transistors (HBT), or Silicon on Insulator (SoI) process. The low noise amplifier is thus not integrated with the power amplifier front end integrated circuit as a complete front end module.
One conventional low noise amplifier design is a single transistor, common source complementary metal-oxide semiconductor circuit, with a tank circuit that is cascoded or connected to the drain of the transistor. Because of the lower transconductance levels of typical CMOS transistors, including n-channel metal oxide semiconductor field effect transistors, increased sizes and higher supplier currents are needed to reach similar gain and noise figure levels relative to bipolar transistor-based amplifier circuits. With a low noise amplifier fabricated with a standard 0.18 μm bulk-CMOS process, biased at 1.8V and having a DC current consumption of 10 mA, a low noise figure of approximately 0.65 dB may be possible, but gain is low, e.g., approximately 9 to 10.9 dB, at the 5 GHz operating frequency.
The latest mobile communication devices require low current consumption together with increase gain in relation to the low noise amplifier to recover losses associated with filters, diplexers, and printed circuit board traces between the antenna(s) and the RF receiver. When current consumption is reduced, however, it is understood that reductions in gain and increases in noise figure will result.
A cascode transistor may be used to improve the gain and input/output isolation, but this is understood to increase noise and require higher bias voltages. In a known cascode transistor low noise amplifier circuit, a bias of 3.3V with a DC current consumption of 10 mA, noise figures may be increased by 0.2 dB to 0.3 dB, with similar gain at the 5 GHz operating frequency as in the aforementioned single transistor circuit.
Accordingly, there is a need in the art for a low noise amplifier circuit with improved noise figure and increased gain. There is also a need in the art for such low noise amplifier circuits to have reduced current consumption.